Conventionally, devices of this kind have been used and are roughly divided into two categories. (1) two-point supporting systems in which the belt for stretching over the user from his waist to shoulder is fixed at one end thereof to one side of a lower portion of the seat and at the other end thereof to the other side of the seat at an upper portion thereof, and (2) three-point supporting systems which comprise two belts, one belt for fastening around the waist and the other across the shoulder of the user.
The foregoing conventional seat belts, however, never dispense with the buckle which is troublesome to handle; therefore, the user tends to neglect wearing said seat belts. Also, the conventional seat belt is inconvenient to store when unused.